I started off by sketching half of the diadem.
Then I took some tracing paper and an extra fine sharpie and copied the design a bit cleaner. Then I took some carbon paper and traced the design on some white cardstock. Then my trusty xacto knife and I cut it out. Rinse, lather and repeat for the other side, but I made sure to flip my tracing paper to make a mirror image for the other half of the diadem.
I then added the center jewel. My intention is to use this now as a template. I bought some metal mesh which I (hopefully) can figure out how to cut to this shape, then cover it perhaps with some light air dry clay.